1. Field of the Invention
This invention generally relates to a bicycle rear derailleur. More specifically, the present invention relates to a bicycle rear derailleur having a simplified base member.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle rear derailleur.
Typically, a rear derailleur has a base member and a movable member with a chain guide movably coupled to the base member via a linkage assembly. The base member is attached to the frame of the bicycle. The chain guide is configured to move the chain laterally over a plurality of rear sprockets. A spring biases the chain guide to an innermost or outermost position relative to the rear sprockets. A Bowden-type control cable is typically coupled to the rear derailleur and to a conventional shift control device in order to control lateral movement of the chain guide. Pulling the inner wire moves the chain guide against the biasing force of the spring, while releasing the inner wire causes the chain guide to move due to the biasing force of the spring.
The typical rear derailleur usually includes a conventional barrel adjuster mechanism that receives the outer casing of the shift control cable, a conventional stroke adjustment mechanism (e.g. high and low adjustment screws) and/or a conventional angular position adjustment mechanism. These mechanisms are typically coupled directly or indirectly to various parts of the derailleur. In either case, prior derailleurs having such adjustment mechanisms can be relatively complicated, cumbersome and/or expensive to manufacture and assemble due to the number of parts and/or the complexity of the parts needed to properly mount such adjustment mechanisms thereto. Also, the base member of a typical rear derailleur has an internal spring such that the derailleur is mounted in a stationary position relative to the frame during normal use, but can be rotated against the biasing force of the internal spring. This type of base member including an internal spring also requires numerous parts in order to properly support its internal spring between the base member and the frame, further complicating the already relatively complicated structure of typical rear derailleurs.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle rear derailleur. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.